The present invention relates to a current collecting means for a self-propelled aerial cableway system. More specifically, the invention relates to an improvement in the structure of a current collecting means comprising current-carrying cables and current collecting shoes in sliding contact for supplying electrical power to a driving means of a self-propelled carriage.
Self-propelled aerial cableway systems, used for long mountain ascents and to cross canyons and rivers, are well known in various constructions. Such a system is found in U.S. Pat. No. 3,983,978 to Uchiyama et al, wherein a self-propelled aerial carriage suspended by a pair of parallel supporting cables is disclosed. The aerial cableway system shown by Uchiyama et al employs a pair of cables which are used both to support a carriage and to carry electric power to the carriage. A pair of current collecting shoes, supported by a pantagraph mechanism attached to the carriage, are urged against the inner sides of the cable.
While this construction provides a current collecting means which can maintain a good sliding contact between cables and current collecting shoes and provide a steady supply of electric power to the carriage, it requires a high cost because electrically conductive supporting cables, such as locked coil wire ropes, are used. It will further be seen that cable wear may be accelerated by sliding contact with the shoes.
A different construction is shown in U.S. Pat. No. 4,053,035 to the same Uchiyama et al. This patent discloses a self-propelled aerial cableway carriage supported by a supporting cable through a supporting member. Two current-carrying cables are supported by the supporting cable by a series of holders. A pair of current collecting shoes are in contact with the two current-carrying cables. The current-carrying cables are constantly urged toward one another by the holder which is provided with spring characteristics, so as to maintain a contacting position with the current collecting shoes.
This system disclosed in U.S. Pat. No. 4,053,035, is generally able to provide a current collecting means for a self-propelled aerial cableway which is simplified and can supply a steady flow of electric current to a carriage. However, this system has construction difficulties because:
(1) the supporting cable is apt to sway when subjected to lateral wind thereby causing unsatisfactory contact between the current-carrying cable and current collecting shoes;
(2) the dimensional relationship between the supporting cable and the current-carrying cables is difficult to hold constant through the whole cableway because of errors in assembly and manufacturing tolerances of the holder; and
(3) the current-carrying cables as well as the supporting cable are apt to sag in a different ratio.
To overcome the aforementioned disadvantages and difficulties in the prior art, Japanese unexamined patent application publication (Kokai Tokkyo Koho) No. 53-11414, discloses an improved current collecting means for a self-propelled aerial cableway system. This current collecting means for a self-propelled aerial cableway is shown in FIGS. 1 to 3 of the drawings accompanied with the present application.
FIG. 1 shows a cableway system which includes a supporting cable, rope or the like 10 defining a cableway of the system, and current-carrying cables 12 which are disposed substantially parallel to each other and to the supporting cable 10. The current-carrying cables 12 are supported on opposite sides of the cable 10 by means of a bracket 14 with insulators 16 disposed between the supporting cable 10 and the current-carrying cables 12. A self-propelled carriage 18 is suspended by a suspending member 20 from the supporting cable 10 and is fitted with grooved drive wheels 22 (though in FIG. 1 merely a front side wheel is shown) which ride on the supporting cable 10. The carriage 18 is driven by an electric driving means, such as an electric motor 24. A current collecting means 26 is disposed in sliding contact with each of the aerial current-carrying cables 12, so as to supply power for the motor 24.
Each current-carrying cable 12 is held within a groove or cavity 28 formed in an insulating holder 30. The holder 30 is secured to the supporting cable 12 through an arm (not shown).
As shown in FIGS. 2 (A) and 2 (B), conventionally, the current-carrying cable is comprised with hollow cylindrical cable of circular cross-section formed of an electrically conductive material such as copper. The current collecting shoe 34 extends into the bottom opening of the groove or cavity 28 of the insulating holder 30 and is tightly forced against the current-carrying cable 12 so as to maintain a steady supply of power for the motor 24. The current collecting shoe 34 has a lateral dimension less than the width of the cavity 28 in order to permit the shoe 34 to slide smoothly in contact with the current-carrying cable 12 therein, along curved portions of the cable 12. Portions of the shoe 34 are off-center with respect to the cable 12 during movement of the carriage 18 along curved portions of the cableway. This may cause the shoe 34 to wear in an uneven fashion so that its bearing surface is inclined relative to the current-carrying cable 12. Once such an offset occurs, the force urging the shoe 34 against the current-carrying cable 12 tends to hold the shoe 34 in an off-center position, thus making the uneven wear on the bearing surface of the shoe 34 progressively worse. As a result, if a predetermined maximum depth of wear is used to determine the lifelimit of the shoe, such a limit will be reached sooner than if the wear is even, as shown in FIG. 5. In addition, as shown in FIGS. 3(A) and 3(B), such uneven wear is generally unsatisfactory. For example, when the carriage 18 is traversing a curved cable portion such that the shoe 34 is off-center in the opposite way to that in which it has principally worn the shoe 34 may make only a line contact at the point represented by the reference letter P in FIGS. 3(A) and 3(B), or similarly make unsatisfactory contact with the cable 12. This may cause arcing and overheating both of which further shorten the life of the shoe.
In view of the foregoing, the present invention is to provide a current collecting means which assures an areal contact between the current collecting shoe and the current-carrying cable to prevent uneven wear of the shoe thereby to maximize the life of the shoe until its predetermined depth of wear is reached and which maintains the shoe in areal contact with the current-carrying cable even in curved portions of the current-carrying cable to maintain a steady supply of electric power.